The overall goal of Core B is to support this POI in all aspects involving RNAi-based knock-down technology. The participating Projects rely to a great extent on cellular systems as platforms for discovery, as well as on our ability to assess gene-function in them. In the absence of genetic approaches for gene ablation in somatic cells, RNAi is the ideal tool for such purpose as a rapid, efficient, inexpensive, versatile, and easy to use method for gene knock-down. Although RNAi approaches also present some challenges, the Core will put in place working strategies to overcome them. Our first aim will be to generate multiple, high-efficiency RNAi-reagents to inhibit the expression of targets that we expect will arise in the course of this PPG as potential regulators of the PTEN-Siah2 pathway. These reagents will be instrumental in evaluating the potential of such regulators as therapeutic targets for the treatment of cancer types derived from PTEN deficiency. To achieve this goal we will systematically generate multiple lentiviral-shRNAs and empirically assess their knock-down potency. The selected reagents will be transduced into the various cell lines and transferred to project teams at various stages of this program. Our second focus will be siRNA screening, as an unbiased tactic to discover new biology surrounding PTEN related tumorogenesis and pinpoint new potential targets. To accomplish these goals, we will provide RNAi libraries, state of the art equipment, expertise and manpower to develop high throughput cell-based assays, execute screens, analyze and confirm results, and produce optimized reagents for follow-up studies. Core B will interact closely with the 3 Projects and Core C, to which it will be providing reagents and services.